1. Field of the Invention
The present invention relates generally to medical care, and in particular to wound therapy and tissue management systems and methodologies with fluid differentiation.
2. Description of the Prior Art
Heretofore, many wound therapy and tissue management devices and protocols have tended to focus on the addition or control of individual mechanical forces and their respective effects on wound healing. For example, the use of suction to secure skin graft dressings in place is disclosed in Johnson, F. E., An Improved Technique for Skin Graft Placement Using a Suction Drain; Surgery, Gynecology and Obstetrics 1984; 159 (6): 584-5. Other prior art devices have focused on the application of compressive (i.e. positive or greater-than-atmospheric) pressure to a wound site, the application of heat and the delivery of pharmacologic agents.
Standard methods in the current practice of wound care require changing the dressing in order to topically add pharmacological agents, which require interval reapplication. Reapplications of pharmacological agents can be minimized or eliminated by using slow-release delivery systems. However, such systems must generally be changed in their entireties in order to change the agents or dosages.
Another wound treatment protocol option involves dosing the entire patient. Agents are thereby delivered systemically, i.e. from within the patient, in order to arrive at the wound site, as opposed to other protocols which deliver respective agents externally or topically. However, systemic medications are generally administered in relatively high doses in order to provide sufficient concentrations in affected areas and treatment sites. Non-affected tissues and organs remote from the treatment sites thus tend to receive concentrations of medications from which they may not benefit.
Fluid management significantly affects many aspects of health care and is involved in many medical procedures. For example, wound care typically involves absorbing and/or draining wound exudates, blood, serum and other body fluids from the patient. Surgical procedures often create wounds requiring tissue management and fluid drainage. For example, skin grafts have exudates and bleeding that require management at both the donor and graft sites. However, current tissue management and fluid drainage procedures are often ineffective in maintaining optimum moisture content for promoting wound healing. Excessive drying, on the one hand, can lead to desiccation, eschar formation and slowing of cell migration. Excessive moisture, on the other hand, can lead to maceration, bacterial overgrowth, tissue breakdown and necrosis.
Various types of porous, absorbent dressing materials have been used for dressing wounds to accumulate body fluids. The dressing materials facilitate drainage and also the collection and disposal of fluids. A disadvantage with many conventional dressings is that they require changing in order to reduce the risk of infection and to maintain effectiveness. However, dressing changes can add significantly to treatment costs and are associated with patient discomfort and medical risks such as infection and damage to reepithelialized tissues. Accordingly, vacuum sources have been employed to drain wounds. For example, Zamierowski U.S. Pat. No. 4,969,880; No. 5,100,396; No. 5,261,893; No. 5,527,293 and No. 6,071,267 pertain to wound dressings, fluid connections, fastening systems and medical procedures utilizing same in connection with vacuum-assisted wound drainage, and are incorporated herein by reference.
A wound drainage device using a hand-operated suction bulb is shown in the George et al. U.S. Pat. No. 4,392,858. Motorized suction pumps can be employed to provide consistent, sub-atmospheric vacuum pressure for maintaining an effective drainage flow. The Richmond et al. U.S. Pat. No. 4,655,754 and No. 4,826,494 disclose vacuum wound drainage systems which can be connected to motorized vacuum pumps.
Another important objective in designing an effective wound drainage system is to provide an effective interface with the patient. Ideally, the patient interface should accommodate various types of wounds in different stages of recovery for as broad a range of applications as possible. As noted above, optimum wound healing generally involves maintaining a sufficient moisture level to avoid desiccation without causing the wound to macerate from excessive moisture. Sufficient moisture levels are required for epithelial cell migration, but excessive moisture can inhibit drying and maturation of the epithelial layer. Pressures should be sufficient for effective drainage without creating excessive negative forces, which could cause pressure necrosis or separate freshly-applied skin grafts.
Wound treatment procedures can also include infusing wound sites with liquids to flush contaminants, counter infection, promote healing growth and anesthetize the wound. Prior art fluid delivery systems include a device for treating tissues disclosed in the Svedman U.S. Pat. No. 4,382,441; a product and process for establishing a sterile area of skin disclosed in the Gross U.S. Pat. No. 3,367,332; and the transdermal infusion device disclosed in the Westin U.S. Pat. No. 4,605,399. Equipment has also been available which flushes and collects contaminants from wounds.
Heretofore, there has not been available a system or methodology that allowed the manipulation of multiple mechanical forces affecting wound surfaces. Moreover, there has not previously been available a system or methodology that manipulated the gradients of gases, solids, liquids and medications in such a way as to provide the medical practitioner with various options for delivering various agents either systemically from the patient side or topically from the external side of a wound. Further, there has not been available a system or methodology which affected the removal of toxins and undesirable byproducts by an external egress with the advantages and features of the present invention. Such advantages include minimizing or eliminating dressing changes whereby patient discomfort and infection risks are correspondingly reduced.
Effective control of fixation, temperature, pressure (and its associated gradients for vital gases such as oxygen), osmotic, and oncotic forces, electrical and electromagnetic fields and forces and the addition and/or removal of various nutrients and pharmacological agents have not been achievable with the previous systems and methodologies. Still further, there has not been available a wound treatment system and methodology utilizing a transfer element for the manipulation of gas and liquid pathways under the control of pre-programmed, coordinated influx and efflux cycles. Such cycles are designed to maintain the desired integrity and stability of the system while still allowing variations in multiple forces, flows and concentrations within tolerated ranges. The previous wound treatments also tended to lack the dynamic and interactive features of the present invention whereby various gradients can be adjusted in response to patient wound site conditions. Such gradient adjustments can be accomplished with the present invention through the use of biofeedback loops and patient-responsive sensors.
Osmotic and concentration gradients provide an important mechanism for transferring various elements within the scope of the present invention. Such gradients occur naturally in living organisms and involve the movement of solutes from solutions with greater concentrations to solutions with lesser concentrations through semi-permeable membranes. Osmosis is the tendency of solids to pass through semi-permeable membranes into solutions of higher concentrations in order to achieve osmotic equilibrium. Diffusion occurs from an area of higher concentration or partial pressure to an area of lower concentration even without membrane separation. Examples include the diffusion transfer of oxygen from alveoli to capillaries within the lung and the osmotic transfer of toxins and waste within the kidneys from capillaries to tubules and on to the bladder. The systems and methods of the present invention utilize and control osmotic and diffusion gradients to advantage in treating wounds, particularly in connection with the removal of toxins and solution from wound sites by controlling fluids. The control of fluids originates both internally and externally. For example, wound exudates originate internally. External control fluids include sumped air, irrigation, etc.
Previous wound treatment systems and methodologies did not provide medical practitioners with the range of options available with the present invention for treating various patient circumstances and conditions.